#include <stdio.h>

void mystrcat(char *a, char *b) {
    while (*a) {
        a++;
    }
    while (*b) {
        *a++ = *b++;
    }
    *a = '\0'; // 添加字符串结束符
}

int main() {
    char a[500] = "Hello ",b[] = "China! ";
    mystrcat(a, b);
    printf("%s\n", a);
    return 0;
}
